/Engine/Source/Editor/PlacementMode/Public/PlacementModeModule.h
Registers system-level (not user) filtering for placeable items. An item is displayed if at least one of the predicate returns true or if there's none registered.
False on failure to register the predicate because one already exists under the specified owner name
virtual bool RegisterPlaceableItemFilter ( [TPlaceableItemPredicate](API\Editor\PlacementMode\IPlacementModeModule\TPlaceableItemPredicate) Predicate, [FName](API\Runtime\Core\UObject\FName) OwnerName )